Elevators are normally allocated based on two allocation methods: continuous allocation or immediate allocation.
In continuous allocation a passenger places a call by pushing an up/down button. With continuous allocation one cannot know for sure how many passengers are actually waiting behind a single call. The number of passengers waiting behind a landing call may be estimated, for example, by multiplying the estimated time of arrival to the call with the passenger arrival intensity obtained from historical or forecasted traffic statistics. The result of the multiplication describes the number of passengers waiting behind the call when an elevator arrives to serve the call. Further, in continuous allocation, the allocation decisions can also be changed. For example, if the traffic situation and the estimated time of arrival to a call changes so that the number of passengers behind the call at the moment of serving the call exceeds the available space in the elevator that is currently allocated to the call, it can be allocated to another elevator.
In immediate allocation, a call is allocated to an elevator immediately after the call is registered and the serving elevator is signalized for the passenger or passengers who gave the call. This means that the allocation decision cannot be changed even if the traffic situation and the estimated time of arrival to the call would have changed so that the estimated number of passengers behind the call exceeds the available space in the elevator. Hence, the estimated time of arrival to the call and the historical passenger arrival intensity give a poor estimate for the number of passengers waiting behind the call. In immediate elevator call allocation, the amount of registered calls does not often correspond to the actual number of waiting passengers.
Based on the above, there is a need for a solution that would provide more accurate elevator allocation in a situation where there are multiple passengers behind a single call.